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Archive through March 17, 2019Ourdee30 03-17-19  10:46 pm
         

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Tempest766
Posted on Sunday, March 17, 2019 - 11:12 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

My question at this point is this, The 6v 4 Ah batteries use a 15 amp fuse when running individually. By running them in series should I fuse them for 30 amps?

When you run batteries in series you increase the voltage, but the available current remains the same. If you want to double the available current then you run them in parallel but keep the same voltage of each individual cell. So no, you're still limited to 15A.

There is still something about the configuration that makes me uneasy, but I'm known to be paranoid.
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Ourdee
Posted on Monday, March 18, 2019 - 01:20 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I'm still listening. There is still something about the configuration that makes me uneasy Could be the second microwave unit mounted at the rear of the air box that's not there as a detector?
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Tempest766
Posted on Monday, March 18, 2019 - 02:09 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

@Ourdee -- If I understand your configuration, you want to put batteries of different capacities and different voltages into the same circuit and expect that the available power budget is the sum of the components. Unfortunately power doesn't work that way. Different types of batteries with different chemistries have different internal resistances, and that internal resistance affects the dynamics of the WHOLE circuit.

I can't be more specific, as I'm not a battery expert, but the scenario causes a dull ache at the base of my skull for some reason that I probably knew 30 years ago, but I've numbed those brain cells since then.
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Teeps
Posted on Monday, March 18, 2019 - 12:04 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Tempest766,
After reading your post above @ 8:24pm; you are either a quick study or have an electrical background.
And from my limited knowledge and exposure to said batteries.

I believe this to be the best practice for the use of lithium batteries.
UNLESS THE DOCUMENTATION FOR THE PRODUCT SPECIFICALLY STATES THAT THE BMS MANAGES CHARGING YOU SHOULD USE ONLY A CHARGER SPECIFICALLY DESIGNED FOR THE LITHIUM BATTERY IN QUESTION.
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Tempest766
Posted on Monday, March 18, 2019 - 12:41 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

you are either a quick study or have an electrical background.

Some electrical background. I write software for embedded computer devices, and am sometimes involved in power distribution applications that exist on unmanned vehicles and drones which have very limited power budgets. I need to know just enough to argue intelligently with the EEs whose MO is "how cheaply can we do it?"
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Motorfish
Posted on Monday, March 18, 2019 - 07:20 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I agree with Tempest. From what I remember, batteries should only be paralleled if they are identical. And I also could have maybe been more specific 30 years ago. I’m an Electrician/Motörhead, not an Engineer, and always remember any batteries connected in parallel being identical.
I don’t know if this helps at all, but before doing anything, you should maybe research it further to be safe.
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Mark_weiss
Posted on Tuesday, March 19, 2019 - 07:24 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Tempest766, You bring up good points and thank you for the explanation. I've never seen the innards of one of the Anti-Gravity batteries. At the Shorai booth they did have some disassembled batteries showing both the individual cells (4) and a circuit board that is also internal. Possibly the circuit board contains some sort of charge smoothing hardware? Shorai does provide an external charging port for use with their bespoke charging device. The Shorai charger is able to charge each cell individually but the Shorai representative told me that their charger should only be necessary for batteries that were unused for several months at a time. That said, I've had over four years of successful use so maybe the Uly's charge ripple is not too disturbing for the battery.
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Ramman4x4
Posted on Tuesday, March 19, 2019 - 10:31 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

After converting my dirt bike to a lithium battery (firepower featherweight) a few months ago, I just ordered a featherweight battery for my Uly. It's an 07 model, so 3-phase charging but the battery is supposed to have onboard bms so I suspect it wouldn't care.

I've had mixed results with all types of batteries over the years. At least one AGM lasted 7 years, other AGM only 2. Likewise with car batteries...my interstate truck battery is on year 8 and never hesitates even after sitting for a month. Similar interstate battery in my car only lasted 3 years.

I'll know soon enough if this featherweight is any good.
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